The invention generally relates to axial flow fans for use in cooling systems. The invention relates particularly to airfoils having low Reynolds number, low drag and high lift.
An axial flow fan may be used to produce a flow of cooling air through the heat exchanger components of a vehicle. For example, an airflow generator used in an automotive cooling application may include an axial flow fan for moving cooling air through a liquid-to-air heat exchanger such as an engine radiator, condenser, intercooler, or combination thereof. The required flow rate of air through the fan and change in pressure across the fan vary depending upon the particular cooling application.
To provide adequate cooling, a fan should have performance characteristics which meet the flow rate and pressure rise requirements of the particular automotive application. For example, some applications impose low flow rate and high pressure rise while other applications impose high flow rate and low pressure rise requirements. The fan must also meet the dimensional constraints imposed by the automotive engine environment.
Accordingly, there is a need to provide fans having improved airfoils in the root region (approximately 90,000 Re), the midspan region (approximately 130,000 Re) and the tip region (approximately 200,000 Re) so as to have high lift to drag characteristics.
An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is achieved by providing airfoils that include a leading edge, a trailing edge spaced from the leading edge, an upper surface extending from the leading edge to the trailing edge, and a lower surface extending from the leading edge to the trailing edge. An airfoil designed for a tip region of a blade has a thickness in a range of 3% to 13%, a Reynolds number in a range from 120,000 to 400,000, and a maximum lift coefficient in a range from 1.0 to 1.2. An airfoil designed for a midspan region of a blade has a thickness in a range of 3% to 13%, a Reynolds number in a range from 90,000 to 200,000, and a maximum lift coefficient in a range from 1.4 to 1.6. An airfoil designed for a root region of a blade has a thickness in a range of 5% to 15%, a Reynolds number in a range from 60,000 to 120,000, and a maximum lift coefficient in a range from 1.8 to 2.0.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.